There have been proposed a number of steering lock devices which, for theft protection, function to lock a steering shaft to prevent the manipulation of the same when an ignition key in an ignition key cylinder is turned to a locking position (LOCK) or is withdrawn from the key cylinder. Some of these devices, however, are so designed and constructed that the locking operation thereof can take place upon turning of the ignition key to the locking position and/or the withdrawal of the ignition key from the key cylinder no matter whether the motor vehicle is at standstill or moving. In this type locking device, should the ignition key be turned by accident or mistake to the locking position or be withdrawn from the key cylinder when the vehicle is moving, locking of the steering shaft occurs and the driver will loose control of the vehicle. Of course, this is quite dangerous.